The field of the present invention is auxiliary drive mechanisms for small vehicles employed for reverse running of the vehicle.
Reverse drive mechanisms have long been available. Most conveniently on larger vehicles, the mechanism is driven by the principal source of power through a reverse gear in the transmission. It is less convenient to employ such a reverse drive in a smaller vehicle. A reverse drive mechanism, disclosed in Japanese Laid-open Patent Publication No. 155545/1984, is provided in a transmission system for transferring driving power from an internal combustion engine to the wheels of a small vehicle such as motorcycle.
In this mechanism reverse speed was limited by interrupting the spark discharge of the spark plug at a certain speed. However, since the internal combustion engine of the vehicle is used which has a range of stable running speeds well above the idling speed, the reduction ratio of the reverse mechanism should be high to obtain a low backing speed of the vehicle, preferably below 2 km per hour. For satisfying this requirement, reduction gears become too large to be practical.
Another type of reverse drive mechanism for large motorcycles, described in Japanese Laid-open Publication No. 252079/1985 comprises an auxiliary retractable wheel which is connected to an electric motor by means of a reduction mechanism. This mechanism employs a separate auxiliary wheel. The driving force through the auxiliary wheel is resisted by the power transmission line from the internal combustion engine to the rear wheel which must rotate as the motorcycle is driven in reverse. Moreover, the auxiliary wheel contacts the road surface at a position laterally shifted from the line connecting the front and rear wheels, so that the auxiliary wheel is not efficient for pulling the front and rear wheels. Thus, certain disadvantages have existed with reverse mechanisms on small vehicles such as motorcycles.